KR102351295B1 - Method and apparatus for removing dust from bulk materials, in particular using ionization - Google Patents

Abstract

In particular, in order to remove the dust 11 adhering to the granular particles 4 from the granules 4 , the air in which the granular particles 4 are preferably laminar from the granule collector at the bottom of the granular intermediate container 9 . Up via a flow 32 - in order to avoid as much as possible friction between the granular particles 4 with each other and to avoid the formation of new dust 11 associated therewith - the granular particles 4 again flow under the influence of gravity into an air flow ( 32) It falls down from the outer side and moves until it falls back into the granule collecting part 4 again. At the same time, above the air flow 32 , a negative pressure is applied to suck upwardly the dust released from the granular particles 4 . Both situations can be achieved by applying a particularly controlled negative pressure to the air outlet opening 18 for dust-laden air. In order to facilitate the separation of dust 11 from granular particles 4 , the air in air stream 32 is ionized while or before it reaches granule collector 4 . do.

Description

Method and apparatus for removing dust from bulk materials, in particular using ionization

The present invention relates, inter alia, to the separation of bulk material from dust contained therein, using ionization, in which case the dust frequently sticks to granular particles, among other things, by means of an electrostatic charge.

In plastics engineering above all else, but also in pharmaceutical and food engineering - raw materials in the form of bulk material - for example granules, pulverized materials, coarse powders, etc. - have to be dealt with frequently. For the purposes of this application, all bulk materials are referred to by the shortened term “granules”.

The transport of this very bulk material often takes place by means of pneumatic transport, in particular by means of air transport, in which case the granules are suspended together by air and mostly in air via transport lines. sent to the desired point.

The granules should be as clean as possible and should not be loaded with impurities, in particular in the form of dust, for further processing, for example to be used as raw material in plastic injection molding machines. These impurities in the form of dust may consist of foreign substances which have been added to the granules unintentionally during manufacture or during transport or which may be dust particles of the same material as the granules themselves, but such a situation may not be suitable for subsequent use. Therefore, it may also be undesirable.

Dust or impurities in the form of dust in the meaning of the present specification, preferably whose diameter is at most 1/10 of the diameter of the granular particles, better still at most 1/30, even better at most 1/100, better It should have a particle size that is at most 1/1000.

As such, the general purpose is to separate such granules from the dust components contained therein prior to use.

For this purpose, different techniques can be used, starting from simple sieving and filtering of the transport air through the process of separating the transport air from the granules, to the separation of the fraction by means of a cyclone.

One of the problems that arise in such a case is that not only the dust particles and the granular particles strongly stick to each other, but also the dust particles stick to the device parts such as the transfer line or the granulation container.

Since this strong adhesion is often caused by electrostatic charges, the consequent removal of dust is usually a mechanical action only when this bonding force, above all else the so-called Lorentz force, is released. can be executed by

In principle, the removal of dust is, as is known, for example by grounding of one fraction, the parts which have been charged differently and are thereby attracted, in this case dust particles on the one hand and granules on the other hand. This is possible by discharging each particle.

However, the above method is practically almost impossible when the number of very small particles is very large as in the present case.

It is therefore an object of the present invention to provide a simple and cost-effectively functioning method and apparatus for releasing the bonding force between dust particles and granular particles.

Said object is solved by the features of claims 1 and 17 . Preferred embodiments emerge from the dependent claims.

The problem of the present invention with respect to the method is that - which is generally in a granule collector lying in the ground - is strong enough to move the granular particles upward with an air flow and thereby separate the granular particles from the bottom upwards. This is solved by generating a known air flow.

If, among other things, the flow velocity of an air stream decreases with height - this is the case, for example, when the cross-section of an air stream expands upwards - until gravity prevails and occurs at a certain height position. The upward force acting on the granular particles decreases until the rise of the granular particles in the reversal zone ends - usually outside the airflow cross-section - and the granules fall back into the granule collector.

From there, the granular particles can again reach the interior of the air flow as the air flow continues, and this cycle may also be performed several times depending on how long the air flow is maintained.

With such a separation, as is known - even if the dust particles still stick to the granular particles slightly - in or above the reversal area, among other things, by a corresponding negative pressure, the dust particles are removed from the granules. upward suction becomes possible.

(ionization)

When the air flow is made of ionized air, the above method can receive strong support, because in this case, the ions present in the air flow prevent static charges and dust particles from adhering to the granular particles. Because it can be removed.

Of course, for a gas flow referred to herein as "air flow", another gas may be used which should not be excluded by this reference. However, for cost reasons, air is used for this purpose, preferably ambient air, which is advantageously filtered before ionization.

According to the invention - by means of the corresponding guiding and shaping of the air flow - among other things - it stands out for the fact that during the upward movement the granular particles rub against each other as little as possible, but rather move parallel to each other, since This is because such mutual friction is caused by the abrasion of the granular particles, no other than the abrasion of additional dust in the granules, which must be avoided or removed immediately.

Such a situation is achieved by the fact that the air flow is preferably a laminar flow, but the cross-section of this flow is preferably enlarged, especially during upward progression, this situation being achieved by means of the corresponding shape of the restricting parts. .

In addition, if the granular particles are moving upwards, a situation in which the granular particles collide with a stationary obstacle must be avoided, since even in this case abrasion and thus new dust will be generated. When such a stationary obstacle is above the granule collector, the upward movement of the granular particles is carried out, in particular through the flow velocity of the air flow, such that the reversal region where the majority of the granular particles end their upward movement lies below the stationary obstacle. Controlled.

An upwardly directed air flow on the one hand, and a negative pressure for sucking in dust, which dominates in the upper region on the other hand, can be generated together by a negative pressure applied over the air flow to be generated.

In this case, the upwardly directed air flow is such that in the cross-sectional area of the air flow most of the granular particles, substantially all of the granular particles, from their starting position to a certain section, ie to the reversal area, but preferably only up to this point It is chosen to be strong enough to be transported upwards.

Among other things, the granular particles must not exceed a preset inversion threshold, which may be, for example, the upper end of the inversion region or may also lie above it.

From the point at which the granular particles are captured by the air flow, preferably at most 3%, even better at most 2% of the particles fall downwards as viewed on the cross section of the air flow, and even better ultimately the granular particles does not fall down at all.

(condensed container)

In general, the process of removing dust from the granules is carried out in a granule intermediate container, preferably in a batch manner, in which case there is a granule discharge opening which can be opened and closed at the bottom of the intermediate container.

replenishment:

In the closed granule discharging opening, the batch of granules to be dusted off is provided inside the granule intermediary container and then placed as a granule collecting part and on the bottom of the granule intermediary vessel also having a granule discharging opening, in which case the granule discharging opening is During filling, it is closed by a closing element, for example a closing flap, and the granules are generally likewise placed on the granule discharge opening.

Air for dust-laden air, which can be covered in the upper region of the granular intermediate container, in particular on the upper side, by a sieve which can be penetrated by dust but not by granular particles There is an exhaust opening.

remove dust:

A negative pressure is applied to the air outlet opening, and after the application of the negative pressure, in particular immediately after the application of the negative pressure, the closing element of the granule discharge opening opens against the applied negative pressure, whereby the air flow flows through the granule collector from below to the top, At the same time, the granular particles lying in the cross-sectional area of the air flow move together upward.

However, since the cross-section of the granule discharge opening is chosen to be smaller than the cross-section of the granule intermediate container, the air flow is enlarged after flowing through the granule discharge opening, whereby the flow velocity of the air flow is increased within the core of the air flow and further also in plan view. When observed as a phase, it decreases toward the edge region and is no longer sufficient from a certain height to compensate for the gravitational force acting on individual granular particles.

As such, after the granular particles have reached the reversal region and also leave the core of the faster flowing air flow laterally by random motion, the granular particles fall down again outside the cross section of the air flow. If sufficient space exists on the perimeter for this purpose when viewed in plan view, this space will cause the granular particles to fall down, in the form of a water fountain pointing directly vertically upwards, surrounding the top and sides of the mushroom shape. A particle fountain having a curtain is formed.

In this case, the granular particles displaced upward in the upper air outlet opening and the sieve optionally present therein - and preferably also also the inlet pipe projecting into the free inner cross-section of the granular intermediate container in said upper region - are preferably carried out Since it must no longer be reached, the strength of the air flow, i.e. the initial flow velocity of the air flow, is set relative to the height position of the aforementioned fixed obstacle, so that the reversal area and/or the reversal threshold is placed under obstacles.

However, if, among other things, the air outlet opening and the granule outlet opening have cross-sections of different sizes, application to the air outlet openings, either by means of separate different pressure generators or by fixing the cross-sections described above in such a relation to each other, is applied, however. It is also possible to control the negative pressure applied to the air outlet opening independent of the air flow rate through the granule outlet opening so as to achieve a desired ratio of the applied negative pressure to the flow rate in the granule discharge opening.

The situation in which the air flowing through the granule discharge opening flows preferably laminar is caused, among other things, by the type of air supplied to the granule discharge opening, and in particular the suction process necessary for this purpose is carried out under the granule discharge opening. This is achieved by doing it over as wide an area as possible and from all sides.

In this region, ie below the granule discharge opening, the air used for air flow is also preferably ionized.

Often below the granule discharge opening is arranged a granule final container, which in turn will be provided in its walls with air-through openings of a corresponding size, preferably surrounding, through which air is, of course, It is blocked by materials that pass but not the granular particles, especially filters.

In this case, the pore size of the filter is preferably selected such that dust particles of a size that are present in the ambient air and should not be present directly in the granules are completely filtered out.

An ionizer is then preferably arranged on the outer face of the wall of the final granulation vessel, whereby ionized air molecules are nevertheless produced in the air drawn in from the outside in the interior of the final granulation vessel. Preferably, the ionizer has an ionizer tip, in the wall there is an ionization opening which is externally covered by the ionizer, and in this case the ionizer tip protrudes from the ionizer into the ionization opening but beyond the wall into the interior. does not protrude.

The air stream introduced from the outside may also be guided so that the ionizer, in particular the ionizing tip of the ionizer, is inside the air stream, but preferably continues to be outside the granulation final container.

evacuation:

After the dust has been removed from a batch in the same type and manner as above, the upward flow of air through the granule discharge opening is terminated, or at least all the granules originating from the granule intermediate container are passed through the granule discharge opening and down , the granules intermediate container is emptied, mostly dropping to such an extent that it falls inside the granule final container arranged below it.

The continuous operation is achieved by permanently supplying a prescribed amount of granules per unit time to the granule intermediate container and setting the air flow so that always a small fraction of the granular particles fall down through the granule discharge opening as opposed to the air flow.

However, such continuous operation has the disadvantage that during operation the granule intermediate container is never emptied as in batch mode operation, and therefore batch mode operation has the following advantages:

Scavenging:

Before filling the granule intermediate container with the next batch, the empty granular intermediate container is purged with ionized gas, in particular ionized air, in order to remove dust particles still present in the granulation intermediate container and adhering, among other things, to the inner surfaces of the walls and floor. can be scavenged.

For this purpose, ionized air flows into the interior of the granular intermediate container, preferably until the granular intermediate container is completely filled with the ionized air and the ionized air has reached all the dust particles present inside the granular intermediate container. In this case the granule outlet opening is normally closed, preferably also the granule inlet opening.

Then, a negative pressure is applied to the air outlet opening of the granule intermediate container, preferably with the granule outlet opening open, whereby the air is suction filtered, usually together with the electrically neutralized and decomposed dust particles.

The process may also be run several times in succession. The period of introducing the ionized gas for scavenging is each from 2 seconds to 20 seconds, in particular from 3 seconds to 10 seconds.

For this purpose, preferably through a separate air inlet for the ionized air, the ionized air is actively - ie by means of a static pressure relative to the pressure inside the granule intermediate vessel, in which the ambient pressure generally prevails in such a state - The granules are introduced into the intermediate container.

Alternatively, ionized air generated below the granule-discharge opening, ie preferably in the granule final container therein, may also be introduced into the granule intermediate container upwards through the opened granule discharge opening, but preferably This situation likewise occurs by means of a static pressure, in order to arrive at the process of first completely filling the granulation intermediate vessel with ionized air before suction filtration through the air outlet opening.

In general, at least 10 liters, better at least 20 liters, still better at least 30 liters, even better at least 35 liters, even better, of at least 10 liters per 10 liters volume of the granular intermediate container to be evacuated. Scavenging should be done with at least 50 liters of ionized gas.

The negative pressure in the air outlet opening may be generated by a conventional negative pressure generator such as a blower, or the negative pressure may be generated by compressed air in the suction line and for this purpose the compressed air and the ionized air and/or the granules are transported. This can be generated by all of the air for evacuation preferably being withdrawn from the same compressed air source and adapted to the respective consumption point only via a pressure reducing valve to the requisite pressure, in particular adapted for the air to be ionized.

In order to carry out the dust removal method described heretofore, it is first necessary - as is customary for batch processing - an apparatus comprising a granule intermediate container, in which case the granule intermediate container has a granule inlet opening and a granule outlet opening and furthermore has an air outlet opening for removing air together with the dust to be removed, in particular for suction filtration.

The granule inlet opening and/or the air outlet opening are naturally in the upper region of the granule intermediate container, in particular in the upper half or in the upper third, and the granule outlet opening in the lower region, in particular in the lower third, of the granule intermediate container. at the point or preferably on the floor.

According to the invention, this device, as described above and directed upwards, starts in or better below the granule collector, more particularly at the bottom of the granule intermediate container, and in particular passes through the granule discharge opening. and an air flow generator capable of generating a preferably laminar flow of air proceeding from bottom to top.

Alternatively, the air flow can also be supplied through a closing element for the granule discharge opening, for example a closing slide, although this makes it difficult to generate a laminar flow.

Preferably, the air flow should be able to expand in an upward direction with respect to its cross-section. As such, the granule discharge opening preferably becomes, at its widest point, much smaller than the horizontal cross-sectional area of the interior space of the granule intermediate container, preferably much smaller than the circular cross-sectional area.

Due to this, the air flow traveling through the granule discharge opening from bottom to top can be enlarged above the granule discharge opening, whereby the flow velocity is caused to move the granular particles against gravity at a certain height, in the so-called reversal area, or It will automatically decrease as the magnification increases, until it becomes too small to remain at the same height.

In this case, the bottom of the granule intermediate container on which the granule collecting part is placed in the filled state is preferably not flat, but rather has an inclined surface in the lower region, so that the cross section of the granule intermediate container gradually narrows downwards as a result. , which narrows in particular conically and preferably ends in a centrally arranged granule discharge opening in the free cross-section of the granule collection vessel.

Due to this, the part of the granule collector lying outside the granule discharge opening, comprising the granular particles falling down again from the raised state, slides in the direction of the granule discharge opening, consequently over time all the granular particles of the granule collector is captured by the air flow and moved upward.

The air flow generator is preferably downstream, more specifically above the air exhaust opening, which may for example be a compressed air ejector nozzle or may be a blower downstream of the granule discharge opening.

The air flow generator is preferably in particular with respect to the intensity and/or duration of the air flow and the starting and ending points of the air flow by means of a control device which is also capable of controlling all other active components of the device as well. can be controlled. In particular, the control of the opening timing of the closing element of the granular discharge opening should be controllable relative to the starting point of the air flow, in particular relative to the starting point of the negative pressure downstream of the air exhaust opening.

Below the granule outlet opening there is a large-area air inlet for ambient air to be drawn in for air flow. Preferably, below the granule discharging opening is a granule final container in close connection with the granule intermediate container except for the closable granule discharging opening.

The air inlet is then preferably in the likewise cylindrical wall, and the granule final container is preferably formed as a surrounding or almost completely surrounding air inlet. The air inlet is preferably covered by a filter, on the one hand to ensure that no dust particles are drawn together from the surroundings and on the other hand to prevent the discharge of the granular particles from the granulation final container.

The apparatus preferably comprises at least one ionizer, which is arranged to ionize the air of the air stream before the air of the air stream reaches the granular particles.

Preferably, the ionizer is arranged on the outer side of the wall of the final container for granulation in the upper region of the final container, in particular above one or more air inlets in the wall of the final container for granulation, and ionizes the internal air. Ionizers generally have through openings within which are ionizing tips which do not protrude into the interior of the granule final vessel. The through-opening may be covered by an ionizer, or ambient air passing through the through-opening along the ionizing tip and entering the granulation final container is actively - in some cases preventing dust particles from being transported from the outside. After being sufficiently filtered for - it can be fed.

Preferably, in the granular intermediate container, in particular in the wall of the granular intermediate container, there is an additional air inlet opening, through which an ionized gas, preferably ionized, to evacuate the granular intermediate container. The compressed air may be introduced into the granule intermediate container.

Preferably, in order to be able to observe the processes taking place inside, the granule intermediate container has a visible window or is made of a transparent material, for example glass, in relation to the entire wall.

In order to ensure that no pressure loss can be achieved on the one hand through the transfer line in the closed state and on the other hand so that in the desired case ionized gas, in particular ionized air, is discharged only through the air outlet opening. For this purpose, a closing element, for example a pinch valve, is preferably arranged in the supply line for the granules which opens into the granule inlet opening.

For compact and compact construction of the device, granular intermediate containers with a volume of less than 5000 cm 3 , in particular less than 3000 cm 3 are used.

In such an intermediate container for granules, granules are usually filled in batches of 300 to 600 ml and dedusted.

Many of the relevant components, and also many of the movable components, are eg shut-off valves in the gas supply, ionizers, shut-off valves in the granulation conveying line, filling in the final granulation container and/or in the granular intermediate container. The level sensor is connected to a control device that receives a signal from the sensor and controls the active components.

Sensors include one or more fill level sensors, respectively, in the granular intermediate container and/or in the granule final container, such as a pressure sensor at different points, such as in the air outlet opening or in the granular final container, and/or in the reversal region of the granular particles. and/or sensors capable of detecting the height position of the reversal threshold, for example a motion detector arranged at a specific height position in the granule intermediate container and in the granule intermediate container.

An embodiment of a device for removing dust from granules according to the invention is described below in various functional states with reference to exemplary drawings. in the drawing section,
1a shows the apparatus for filling an intermediate container of granules in a partially vertical cross-sectional view, FIG.
Figure 1b shows a cross section taken along the line Ib-Ib of Figure 1a;
Fig. 2a shows the apparatus for removing dust from the granules in the granule intermediate container, partially in vertical sectional view,
Figure 2b shows a partially enlarged cross-sectional view of Figure 2a,
3 shows the apparatus for emptying the granule intermediate container in a partially vertical sectional view, FIG.
Fig. 4 shows the apparatus for evacuating an empty granular intermediate container, partially in vertical section, and
FIG. 5 shows, in partial vertical sectional view, an apparatus for suction filtration of scavenged gas from a scavenged granular intermediate vessel; FIG.

The dust removal of the granules 4 takes place in a batchwise manner in the granule intermediate container 9 .

Therefore, in a first step, as shown in FIG. 1A , the granule intermediate container 9 is filled with a batch of granules 4 .

For this purpose, a suction lance 16 is inserted into the storage of granules 4 in the storage container 7 . a storage vessel, via a transfer line 15 connected to the suction lance 16 , the other end of which ends in an inlet tube 24 , the open free end of which forms a granule inlet opening 8 in the granule intermediate vessel, The granules from the are transported by conveying air 3 flowing in the flow direction 10 and moving together with the granular particles 4 .

Here, the inlet pipe 24 flows closely through the wall of the granular intermediate container 9 and its free end is an angled pipe member pointing downward in the granulating intermediate container 9, resulting in a conveying line 15 . The granules 4 supplied via (8) flows downward.

The granules 4 transported therein are deposited in the form of a granule depositing section 4 at the bottom of the granule intermediate container 9 . For this purpose, the granule discharge opening 25 at the bottom of the granule intermediate container 9 is closed.

The conveying air 3 leaves the granule intermediate container 9 via its outlet opening 18, in which case the outlet opening is arranged in the cover of the granular intermediate container 9 in a conical shape which tapers upwards and gradually narrows. , a sieve 5 can be draped over it, which can be overrun by the conveying air 3 and by the dust 11 contained in the conveying air as the case may be, but with granular particles 4 . cannot be perfused by

From there, the conveying air 3 flows along the dust line 20 in its flow direction 10 to the dust collection container 12, into which the dust line 20 is open, The conveying air 3 can leave the dust collection container through an exhaust air filter 2 arranged on the cover 27 of the dust collection container 12 in the exhaust opening, but the exhaust air filter 2 cannot pass through. The dust 11 without it cannot escape.

The flow of conveying air 3 is caused by a negative pressure generator downstream of the air outlet opening 18 , in particular downstream of the sieve 5 , in this case arranged downstream of the exhaust air filter 2 , This is caused by an ejector compressed air nozzle 21 , which may also be arranged downstream of the air outlet opening 18 directly in the dust line 20 .

These ejector compressed air nozzles 21 shoot compressed air - mostly drawn from the existing stationary compressed air network - into individual transport lines in the desired flow direction 10 , thereby downstream of the ejector extruded air nozzles 21 . creates a negative pressure in the transport line, whereby the transport air 3 flows in the flow direction 10 .

The ejector compressed air nozzle 21 operates until sufficient granules 4 , ie the desired quantity of batches, are present in the granules intermediate container 9 , then compressed into the ejector compressed air nozzle 21 . The air supply is terminated, preferably the transfer line 15 is also closed by means of a shut-off valve 35 , in particular by a pinch valve 35 .

It becomes clearer in the cross-sectional view of FIG. 1 a that the granule collection container 9 is a vertically standing substantially cylindrical container, ie a container with rotationally symmetrical walls, which in the lower region are centered on its inner center. They approach each other in the shape of a cone 28 up to the arranged granule discharge openings 25 . The free lower end of the cone 28 is a granule discharge opening 25 which can be closed by means of a closure flap 6 and is closed during filling of the granule collection container 9 . The closing flap 6 is opened and closed by means of a pneumatic cylinder 23 .

As can be seen in FIG. 1b , in particular the area of the circular granule-discharge opening 25 can be much smaller than the area of the in particular circular inner free cross-section of the granule intermediate container 9 , in particular the circular granule inlet opening 8 . , that is to say, the internal free cross-section of the inlet at the end of the inlet tube 24 may again be slightly smaller, although neither of these circumstances is a condition for implementing the present invention.

Then, as shown in FIG. 2A and in the enlarged view of FIG. 2B , the dust of the batch in the granular intermediate container 9 is removed.

As can best be seen in FIG. 2b , for this purpose, first a negative pressure is created in the dust line 20 , that is to say, for example, compressed air is provided to the ejector extruded air nozzle 21 while the pinch valve ( 35 ) remains closed during the dust removal of granules 4 in the transfer line 15 , immediately after which the closing flap 6 is opened, for which purpose the closing flap has already been removed - the dust line 20 . ) must overcome the built-up negative pressure in the sealed intermediate container (9) of granules.

Due to the negative pressure prevailing in the granule intermediate container 9 , ambient air 31 is drawn in from the region below the lower granule discharge opening 25 , through which a substantially laminar flow of air flows through. flows upward in 32 , said laminar air flow initially having, for example, a cross-section of a granule discharge opening 25 , the cross-section of the air flow 32 gradually moving upward with respect to the granule discharge opening 25 . Due to the walls of the granule intermediate container 9 receding back, it can be slightly enlarged going upwards.

In other words, the air flow 32 flows through the granular deposit 4 supported downward by the previously closed closure flap 6 , the granular particles previously lying on the closing flap 6 . (4) does not fall downward through the granule discharge opening (25), but rather granular particles (4) in which the flow velocity in the air flow is guided together therein, due to the enlargement of the air flow (32). has enough force to be transported upwards together at the center of the cross section of the granular intermediate container 9 from the air flow 32 until it is no longer sufficient to keep it rising, or only to keep it in this elevated state. .

As such, the granular particles 4 will mostly end their upward motion, ie by at least 80%, better by at least 90%, at a certain height position, ie in the reversal region 30 , in the central airflow (32) From the lateral side, it falls down again into the outer region of the inner space 14 of the granular intermediate container 9, and falls back into the annular outer edge region of the granule deposit.

However, the granular particles 4 should not, for the most part - in the sense of the above definitions - above all else exceed the preset reversal threshold 30' upwards. The inversion threshold 30' in this case lies above the upper limit of the inversion region 30, but may be the same as the inversion region.

Due to the lower cone 28 , the granular particles slide in the direction of the centerline of the granule intermediate container 9 standing vertically on said cone, and again an upward flow of air in and out of the cross-sectional area of the granule discharge opening 25 ( 32) is approached, and it is newly transported upwards.

In other words, depending on the duration of the air flow 32 , the granular particles 4 pass through multiple cycles as above.

Below the granule discharge opening 25 and thus below the granule intermediate container 9 is a granule final container 14 , likewise mostly a substantially vertical standing cylinder. Said granule final container 14 is mounted on the upper face of a user device 50 for granules 4, which is frequently only shown only in FIG. 1a , and serves as an intermediate reservoir, from which - granule final When the lower opening of the container 14 is opened - the granules are fed to the user device 50 .

On the side wall of the granular final container 14 , air inlet openings 33 for ambient air 31 are formed over a large area, but these air inlet openings are, so that dust does not reach the inside of the granulation intermediate container 14 and from there, due to the negative pressure prevailing in the granulation intermediate container 9 , it does not reach upwards into the granular intermediate container 9 and does not reach the air flow 31 . For this purpose - preferably annular over the entire perimeter of the granulation final container 14 , it is covered by a feed air filter 133 .

The suction filtered ambient air 31 is ionized by an ionizer 37a on its path through the final granulation vessel 14, which ionizer is on the outer face of the outer wall of the granulation final vessel 14, preferably It is preferably arranged directly below the granule discharge openings 25 , but in any case above one or more air inlet openings 33 .

The ionized ambient air 31 causes a partial electrical polarity reversal or neutralization of the dust particles adhering to the granular particles 4 or to the inner face of the wall of the granular intermediate container 9 by an electrostatic charge, and consequently these Dust particles are more easily separated and can be discharged through the dust line 20 and through the sieve 5 .

Another ionizer 37b , which is arranged on the outer side of the wall in the granule intermediate vessel 9 and shown in the figure, can preferably also be operated during dust removal of the granules 4 , but in this case preferably with laminar air flow. In order not to adversely affect flow 32, it can be operated without air flow through gas inlet 36b there.

After the dust removal of the granules has been carried out for a sufficient time, the dust removal process is finished, and according to FIG. 3 , it passes through the granule discharge opening 25 in an open state and downwards inside the final container 14 of the granules. By falling into the , the granule intermediate container 9 of the granules 4 is emptied.

For this purpose, only the negative pressure in the suction line 20 needs to be terminated, more specifically, only one or more ejector compressed air nozzles 21 need to be switched off, ie only the supply of compressed air needs to be terminated.

The now empty granular intermediate container 9 is, as can be seen with reference to FIGS. 4 and 5 , now removed, among other things, from dust that has settled on the inner surface of the wall of the granular intermediate container.

For this purpose - as shown in FIG. 4 - the granulation intermediate vessel 9 is evacuated with ionized air 34, in which case the closure flap 6 preferably remains closed.

However, the ionized air 34 is not normally generated by the first ionizer 37a arranged in the granulation final vessel 14 , but rather on the outer wall of the granular intermediate vessel 9 , preferably at the bottom of the vessel. It is generated by the second ionizer 37b arranged in the region.

The second ionizer is flown through by air, in particular by compressed air supplied via a compressed air line 26 . After ionization while passing through the ionizer 37b, compressed air is introduced into the granular intermediate container 9 through the air supply opening 36 .

However, the first ionizer 37a is usually not perfused by air, but rather by its own ionizing tip - the granulation final vessel 14 opens the air supply opening 36 similarly to the granule intermediate vessel 9 . As formed - only protrude into the through opening in the wall of the granulation final vessel 14 but only into the through opening to such an extent that the ionizing tip does not protrude inward into the vessel, in this case into the granulation final vessel. do.

The ionizing tip of the second ionizer 37b , which is further perfused with air, can likewise be arranged in the through opening, in this case the air supply opening 36 .

In particular, the two ionizers 37a, 37b may be formed identically and arranged similarly, and the air supply to the individual ionizers 37a, 37b may be made or cut off as required. In the individual compressed air lines 26 to the ionizers 37a, 37b, there may also be one pressure regulating valve 29 each, as shown only in FIG. 2A .

After the granulation intermediate container 9 is completely filled with ionized air and while the ionized air 34 continues to be supplied, - as shown in FIG. 5 - a suction line ( 20), the ionized air concentrated into the separated dust is suction filtered while passing through the upper gas outlet opening 18 and the dust line 20 of the granular intermediate vessel 9 from the granular intermediate vessel 9. It is supplied to the dust collection container (12).

In this case, the granule discharge opening 25 is open at the bottom of the granule intermediate container 9 in order to enable the suction of ambient air through the granule final container 14 .

For the purposes of the present invention, the negative pressure can also be generated by other suitable negative pressure generators, in particular blowers, instead of the ejector compressed air nozzle 21 .

Thus, the granule intermediate container 9 and the entire apparatus can be used to process the next batch of granules 4 .

All the processes described above are controlled by the central control unit 22:

The central control unit, via the compressed air line

- on the pinch valve (35);

- at least in the second ionizer 37b,

- on the pneumatic cylinder 23 for moving the closing flap 6, and

- to one or more ejector compressed air nozzles (21) for the purpose of generating negative pressure;

Compressed air is supplied under controlled conditions with respect to quantity and time.

Furthermore, the central control unit controls the filling level sensor ( 9 ) in the granule final container 14 and in the granule intermediate container 9 , for example to end the filling process at the correct time, according to the measurement signal of the filling level sensors. 19a, 19b) and signal technically connected.

In addition, the two ionizers 37a, 37b are also energized and controlled by the control device 22 .

1: Granule Separator
2: Exhaust air filter
3: conveying air
4: granules, granule collecting part, granular particles
5: Sieve
6: Closing flap
7: storage container
8: granule inlet opening
9: Granule intermediate container
10: flow direction
11: Dust
12: dust collection container
13: supply air filter
14: granulation final container
15: transfer line
16: suction lance
17: compressed air source
18: air exhaust opening
19a, 19b: fill level sensor
20: dust line
21: ejector compressed air nozzle
22: control device
23: pneumatic cylinder
24: inlet pipe
25: granule discharge opening
26: compressed air line
27: cover
28: cone
29: pressure regulating valve
30: inversion area
31: ambient air
32: air flow
33: air inlet opening
34: ionized gas
35: shut-off valve, pinch valve
36a, 36b: gas supply opening
37a, 37b: ionizer
50: user device

Claims (27)

A method for removing dust from granular particles (4), comprising:
- through the granular particles (4) in the granule collector, an air flow (32) which is controllable with respect to its own flow rate and strong enough to carry the granular particles (4) together upwards is guided upwardly,
- the flow rate of the air flow 32 is chosen such that the granular particles 4 guided together in the air flow 32 end their upward motion by gravity and fall downwards below a reversal threshold 30' becomes,
- above said reversal threshold 30', a negative pressure is applied which is sufficient to suction filter the dust 11 contained in the air stream 32 upward, but too weak to suck the granular particles 4 downward;
After removing the dust from the granular particles, the granular intermediate vessel 9, which no longer contains the granular particles, is evacuated with ionized air, wherein:
- the granule discharge opening 25 is closed or closed,
- the blocking element 35 of the transfer line 15 is closed or closed,
- by introducing ionized gas (34) into the granular intermediate vessel (9), and
- characterized in that at the latest from the point at which the granular intermediate vessel (9) is completely filled, the ionized gas (34) is continuously removed from the granular intermediate vessel (9) and evacuated by suction filtration through an outlet opening (18); Way. According to claim 1,
- the air flow (32) is caused by a negative pressure applied above the reversal threshold (30'),
and/or
- The method, characterized in that the cross section of the air flow (32) is formed to increase gradually from the bottom to the top, so that the flow rate of the air flow (32) is selected to decrease gradually from the top. 3. The method of claim 1 or 2,
- such that the granular particles 4 guided together in the air flow 32 move in the direction of the air flow 32 parallel to each other or the air flow 32 becomes a laminar air flow 32; A method, characterized in that a flow (32) is generated and guided. 3. The method of claim 1 or 2,
In the case of the granule collecting unit
- when viewed from above, the cross-section of the air flow (32) flowing through the granule collector is smaller than the cross-section of the granule collector;
and/or
- The method, characterized in that the granular particles (4) falling down are again fed to the granule collector. 3. The method of claim 1 or 2,
The air flow 32 for removing dust from the granular particles is such that each granular particle 4 is guided together upward by an air flow 32 several times and then fed back to the granule collector by gravity. A method, characterized in that it occurs frequently and/or for such a long time. 3. The method of claim 1 or 2,
The air flow 32 is such that, before the air flow 32 reaches a stationary obstacle outside the granule collector, the granular particles 4 guided together within the air flow end their upward motion by gravity. A method, characterized in that it is selected so strongly. 3. The method of claim 1 or 2,
A method, characterized in that the air in the air stream (32) is ionized before the air stream (32) reaches the granule collector. 3. The method of claim 1 or 2,
A method, characterized in that after dust has been removed from the batch of granules, the air flow (32) is either terminated or at least reduced to such an extent that the granule collector falls downward through the granule discharge opening (25). 3. The method of claim 1 or 2,
Method, characterized in that air for the air stream (32) is supplied to the air stream (32) below the granule collector. 3. The method of claim 1 or 2,
Dust removal is carried out in the granulation intermediate container (9),
- at the bottom of the granule intermediate container there is a granule discharge opening 25, under which the supply of ambient air 31 is made or a granule final container 14 is arranged,
and/or
- in the upper region of the granular intermediate container there is an exhaust opening 18 for dust-laden air, in which there is a sieve 5 through which the granular particles 4 cannot pass, said Method, characterized in that the intensity of the air flow (32) is set such that the granular particles (4) do not reach the outlet opening (18). 3. The method of claim 1 or 2,
The granular intermediate container 9 is filled with a new batch of granules by means of an air transfer flow in a transfer line 15 that is open into the granular intermediate container 9, and while the transfer line 15 is dedusting A method, characterized in that it is closed. 3. The method of claim 1 or 2,
- an air transport stream 3 and also a negative pressure generated by the compressed air above the reversal region, and
- the introduced ionized gas 34 is ionized compressed air, and
- a method, characterized in that both are drawn from the same compressed air source (17). 3. The method of claim 1 or 2,
A method, characterized in that the ionized gas (34) is introduced by atmospheric pressure or by a pressure above atmospheric pressure. 3. The method of claim 1 or 2,
- between the dust removal processes of granular particles, the duration of the introduction of the ionized gas 34 for scavenging is 2 to 20 seconds, respectively,
and/or
- Method, characterized in that at least 10 liters of ionized gas (34) are introduced per 10 liters of granular intermediate vessel (9) to be evacuated. delete delete delete delete delete delete delete delete delete delete delete delete delete

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